There is at the present time a need for a small portable field instrument for testing the yoke and flyback transformers of solid state television receivers. In order to locate the cause of a problem in the sweep circuits of a television receiver it was common to substitute a coil of a test instrument for the yoke of the receiver and then to measure the amount of power delivered to the substitute coil. If the substitute coil corrected the problem it was apparent that the yoke was defective. This method is not satisfactory for use with solid state television receivers because of the difficulty of providing a universal substitute yoke which will not overload the sweep circuits.
One method which has been reliably used to test yoke coils and transformer windings is a ringing test. With this testing method a narrow voltage pulse is applied to the coil to cause it to ring, i.e., resonate and produce a dampened sine wave. By analyzing the dampened sine wave as displayed on an oscilloscope it can be determined whether the coil is defective. This is, however, a sophisticated test which requires a highly skilled operator since minor adjustments of the oscilloscope can cause a good coil to appear defective and vice versa. Another disadvantage of this test is the fact that it requires an oscilloscope and is thus not suitable for field use.